Synthesis of nanostructured hydroxides and oxides of iron: Control over morphology and physical properties

This paper reports on the surfactant-assisted synthesis of nanotubes and nanorods of beta-FeOOH and hence alpha-Fe2O3 (hematite) with remarkable stability against temperature under different reaction conditions. Characterization and a comprehensive study of their nanosized properties are carried out by powder X-ray diffraction, thermal analysis, transmission electron microscope, and vibrating sample magnetometer. Upon calcination at 300 degrees C, beta-FeOOH nanostructures transform to alpha-Fe2O3 with some change in morphology. The samples convert to layered rod-like structures and further into some sort of a disc resembling stacked structures upon heat treatment. Even for magnetic fields up to 10 000 G, the magnetization curves for the nanotubes/nanorods of hematite do not attain the saturation magnetization. All the materials exhibit a very low coercivity even at room temperature and hence are potential materials for magnetic applications.